Zirconium orthosilicate (ZrSiO.sub.4), when plasma sprayed onto a substrate, provides an opaque, white surface having reflective, refractory properties. This surface has the potential of being an effective thermal control surface, for preventing overheating from solar absorptivity. The surface can be applied to the outside of structures and inhibits overheating of the structures. The structure can be an enclosure, for instance one containing instrumentation and electronic equipment. The zirconium orthosilicate surface thus inhibits overheating of the enclosure, and whatever equipment is contained within the enclosure. The surface is particularly beneficial in space applications.
However, the zirconium orthosilicate surface, when exposed to X-rays and ultraviolet radiation, darkens. This darkening can result in solar absorption sufficient to cause overheating. In the case of instrumentation and electronic equipment, the overheating can be to the point of failure of the instrumentation and electronic equipment.